Various types of ion sources may be used to create the ions that are used in semiconductor processing equipment. For example, in certain embodiments, a spot beam may be created by an ion source. A spot beam is one in which the ions are transported as a beam having a substantially circular cross-section. This spot beam may enter an electrostatic scanner. The electrostatic scanner deflects the spot beam at varying angles in a first direction. For example, in certain embodiments, the electrostatic scanner may deflect the spot beam in the horizontal direction. The amount of deflection may be at least as large as the diameter of the workpiece that is being processed by the spot beam. In this way, ions are implanted into the workpiece across its entire width. Typically, the workpiece is disposed on a movable workpiece holder, which is moved in a second direction. This second direction may be perpendicular the first direction. In some embodiments, the workpiece holder translates the workpiece in the vertical direction. In this way, the entirety of the workpiece may be processed. In other words, the spot beam is deflected back and forth in the first direction, while the workpiece is translated in the second direction.
One issue associated with the use of a spot beam is non-uniformity of the ions in the first direction. Specifically, the dose implanted in the workpiece may vary as a function of position in the first direction. This may be due to non-uniformities in the electrostatic scanner.
Conventionally, this non-uniformity is corrected prior to implantation. For example, a beam monitor, such as a plurality of Faraday cups may be disposed downstream from the electrostatic scanner. The beam monitor determines the number of ions as a function of the position in the first direction. Based on this, the scan rate of the electrostatic scanner may be modified so that the resulting beam is uniform in the first direction. Stated differently, the scan rate of the electrostatic scanner may be made non-uniform in order to achieve uniformity of the dose delivered to the workpiece. This may be referred to as the first stage of the process to achieve a desired two-dimensional dose. This first stage achieves a uniform dose in the first direction.
Once the non-uniformity of the spot beam in the first direction has been corrected, the second stage of the process is initiated. In the case of a patterned implant, the second stage may involve adjustments to the scan rate of the electrostatic scanner as a function of position in the second direction. For example, the desired implant pattern may not be uniform in at least one of the first or second direction. Thus, the second stage of the process uses the desired implant pattern to determine the scan rate in the first direction as a function of position in the second direction.
Thus, in order to implant ions into a workpiece using a spot beam, a uniformity tuning process that achieves beam uniformity in the first direction is performed. This process is time consuming and lowers overall utilization of the ion beam implanter.
Thus, it would be advantageous if there were a system and method that generated the desired implant pattern in a workpiece without having to perform the uniformity tuning process.